Generally, a railroad includes at least one pair of elongated, substantially parallel rails coupled to a plurality of laterally extending ties which are disposed on a ballast bed. The rails are coupled to the ties by metal tie plates and spikes and/or spring clip fasteners. The ballast is a hard particulate material such as, but not limited to, gravel. Ties may be made from either concrete or wood. The ballast filled space between ties is called a crib. Concrete ties are typically spaced about twenty-four inches apart, whereas wood ties are spaced about nineteen and a half inches apart. However, ties may be “skewed” relative to the rails. That is, the ties may be crooked and not extend generally laterally, i.e. perpendicular to, the rails.
During installation and maintenance of the railroad, the ballast adjacent and/or under the ties must be “tamped,” or compressed, to ensure that the ties, and therefore the rails, do not shift. While it is the ballast material that is being tamped, it is common to refer to this operation as tamping a “tie.” It is understood that tamping, or otherwise having a tamper assembly engage, a “tie” means that the ballast adjacent/below the indicated tie is being tamped/engaged. As used herein, the tie(s) which are being tamped/engaged shall be identified as a “worksite tie.” When the tamper vehicle advances, another tie becomes the “worksite tie.”
A tamping device, and/or the vehicle that supports the tamping device, is called a “tamper.” As used herein, the vehicle supporting the tamper shall be identified as the “tamper vehicle.” The tamper vehicle typically supports at least a pair of tamper assemblies. Each tamper assembly typically consists of one pair of workheads. A workhead includes at least two vibration devices each with a pair of elongated, vertically extending tools structured to move together in a pincer-like motion as well as being structured to move vertically. The vertically extending, and more specifically, vertically descending tool may have a single prong or multiple prongs. A vibration device is coupled to each tool and is structured to vibrate each tool. As the tools are structured to move together in a pincer-like motion, the tools of each of the workheads are disposed on opposite sides of a tamper assembly centerline. In this configuration, a workhead may be disposed above a worksite tie with one or more tools on either side of the rail at the worksite tie.
Because it is desirable to tamp the ballast on both the inner and outer sides of the rail, each of the workheads may have two adjacent pairs of tools; one tool disposed on the outer side of the rail, and one tool disposed on the inner side of the rail. In this configuration, the tools disposed on one side of a worksite tie may share a vibration device.
Thus, a tamper assembly is structured to engage the ballast at eight locations at each worksite tie; one tool set engages the forward side of the tie on the outer side of the rail, one tool set engages the rearward side of the tie on the outer side of the rail, one tool set engages the forward side of the tie on the inner side of the rail, one tool set engages the rearward side of the tie on the inner side of the rail. This is repeated on the tie/rail intersection of the opposite side.
In another configuration, a workhead may be disposed above a rail with one tool set on either side of the worksite at the rail. In this configuration the tools on the outside of the rail are driven by one vibrator, while the tools on the inside of the rail are driven by a separate vibrator. This is also repeated on the tie/rail intersection of the opposite side.
Initially, the tools are generally vertical and parallel to each other. When actuated, each workhead moves vertically downward so that the tips of the tools, that are the lower, distal ends of the prongs, are inserted into the ballast to a predetermined depth. The depth is, preferably, below the bottom of the tie. The tools are then brought together in a pincer-like motion thereby compressing the ballast under the tie. Actuation of the vibration device further compresses the ballast under the tie. Once the vibration operation is complete, the tools are returned to a substantially vertical orientation and lifted out of the ballast. The tamper vehicle then advances to the next worksite tie and the operation is repeated. Typically, a tamping operation lasts about three seconds.
Some tamper vehicles use more than one pair of tamper assemblies. That is, one pair of tamper assemblies is disposed forward but adjacent the other pair of tamper assemblies on the tamper vehicle. When there are two pairs of tamper assemblies, and if one were to alternately identify the ties in a series of ties as being “odd” or “even” ties, one pair of tamper assemblies tamps the “odd” ties and the other pair of tamper assemblies tamps the “even” ties. Thus, multiple ties may be tamped at one time.
Where there are two pairs of tool heads, two configurations are commonly used. In one configuration, as identified above, the two pairs of tamper assemblies are disposed adjacent each other on the same tamper vehicle body. In this configuration, the two pairs of tamper assemblies typically operate on adjacent ties. One problem with this configuration is that when the ties are disposed too close to each other, or when one tie is skewed so that one end of a tie is close to an adjacent tie, the two pairs of tool heads may not fit into the space above the ties. If this happens, the operator must disengage one of the two pairs of tool heads and tamp the ties individually. These problems are typically encountered with wood ties.
In another configuration, the second pair of tool heads is disposed on a “chase” vehicle. The chase vehicle typically does not include various components associated with a complete tamper vehicle, e.g. a tie locator, track lifting devices, lining devices, clamps, reference system. Further, the chase vehicle typically requires its own tamper assembly operator.